This invention relates generally to the stabilization of biomolecules in solvent systems compatible with electrostatic or electrohydrodynamic aerosol devices, and specifically to the stabilization of biologically active proteins such as insulin in liquid systems.
Pulmonary delivery of therapeutic agents by means of inhaled aerosols is an area of increasing importance in the biotechnology and pharmaceutical industries. Electrostatic or electrohydrodynamic devices which are capable of generating inhalable aerosols with certain preferred properties frequently require liquid formulations containing one or more solvents such as water, an organic solvent such as an alcohol, or a mixture of water and at least one organic solvent.
Biological molecules, (“biomolecules”) are frequently difficult to formulate in certain solvents or solvent systems (e.g., mixtures of water and organic solvents) because organic solvents tend to compromise the stability of the biomolecule in solution. Biomolecules dissolved or suspended in liquid solvent systems typically suffer from chemical or physical degradation, thereby resulting in a formulation with little or no shelf life. Stabilization of the biomolecule in a given solvent system is therefore necessary to sustain the activity a given biomolecule. In formulations for use with electrostatic or electrohydrodynamic aerosol devices, non-ionic stabilizers are preferable to ionic compounds.
Regarding proteins used in pharmaceutical applications, processing and storage conditions, which do not diminish a given protein's biological function, must be achieved. To prevent the loss of native conformation, proteins must be protected from the chemical decomposition (e.g. by deamidation) and physical instability, which results from the disruption of noncovalent interactions. Aggregation (fibrillation), precipitation, and adsorption (especially on hydrophobic surfaces) are examples of such disruption.
One of the most important and commonly used therapeutic proteins is insulin. Insulin tends to polymerize and form microscopic aggregates, which prevent the delivery of insulin in certain drug delivery systems. This aggregated insulin may not have required pharmacological properties and may induce abnormal immune response (Chawla et al., Diabetes 34: 420–425, 1985). Thus, maintenance of insulin's biological activity is essential for more traditional insulin administration such as portable/implantable continuous infusion pumps and controlled release polymeric devices and systems. Furthermore, insulin aggregation leads to significant reductions in biological potency and obstruction of delivery routes, thereby creating serious complications for drug delivery systems and diminishing the patient's abilities to control their blood glucose levels.“Sluzky et al., Biotechnology and Bioengineering 40: 895–903 (1992). Thus, there is a need for a method for stabilizing insulin and other biomolecules in liquid formulations utilized in drug delivery systems.
Stabilization methodologies for certain biological molecules are known in the art. For example, WO 98/29097 discloses compositions for increasing bioavailabilty through muscosal delivery, which includes mixtures of bioactive agents, and hydrophobically derivatized carbohydrates in powdered form. Similarly, WO 99/33853 discloses derivatized carbohydrates, which can be used to form a variety of materials, including solid delivery systems.
U.S. Pat. No. 4,439,421 issued to Hooper et al. (1984) discloses a stabilized gamma globulin concentrate in dry form, which utilizes polysaccharides including, branched and unbranched polymers of five and/or six carbon sugars. U.S. Pat. No. 5,547,873 issued to Magneson et al. (1996) discloses a composition for stabilizing proteins for long-term dry storage, which includes a glass-forming sugar.
While being effective at stabilizing certain biomolecules under certain conditions, the related art deals primarily with dry power or other solid systems, and do not offer methods or compositions for stabilizing biomolecules in liquid solvent systems suitable for use in liquid-based aerosol systems, including electrostatic and electrohydrodynamic devices and systems.